Over the last few decades revolutionary advances have been made in electrochemical storage and conversion devices expanding the capabilities of these systems in a variety of fields including portable electronic devices, air and space craft technologies, passenger vehicles and biomedical instrumentation. Current state of the art electrochemical storage and conversion devices have designs and performance attributes that are specifically engineered to provide compatibility with a diverse range of application requirements and operating environments. For example, advanced electrochemical storage systems have been developed spanning the range from high energy density batteries exhibiting very low self-discharge rates and high discharge reliability for implanted medical devices to inexpensive, light weight rechargeable batteries providing long runtimes for a wide range of portable electronic devices to high capacity batteries for military and aerospace applications capable of providing extremely high discharge rates over short time periods.
Despite the development and widespread adoption of this diverse suite of advanced electrochemical storage and conversion systems, significant pressure continues to stimulate research to expand the functionality of these systems, thereby enabling an even wider range of device applications. Large growth in the demand for high power portable electronic products, for example, has created enormous interest in developing safe, light weight primary and secondary batteries providing higher energy densities. In addition, the demand for miniaturization in the field of consumer electronics and instrumentation continues to stimulate research into novel design and material strategies for reducing the sizes, masses and form factors of high performance batteries. Further, continued development in the fields of electric vehicles and aerospace engineering has also created a need for mechanically robust, high reliability, high energy density and high power density batteries capable of good device performance in a useful range of operating environments.
Many recent advances in electrochemical storage and conversion technology are directly attributable to discovery and integration of new materials for battery components. Lithium battery technology, for example, continues to rapidly develop, at least in part, due to the discovery of novel electrode and electrolyte materials for these systems. The element lithium has a unique combination of properties that make it attractive for use in an electrochemical cell. First, it is the lightest metal in the periodic table having an atomic mass of 6.94 AMU. Second, lithium has a very low electrochemical oxidation/reduction potential (i.e., −3.045 V vs. NHE (normal hydrogen reference electrode)). This unique combination of properties enables lithium based electrochemical cells to have very high specific capacities. State of the art lithium ion secondary batteries provide excellent charge-discharge characteristics, and thus, have also been widely adopted as power sources in portable electronic devices, such as cellular telephones and portable computers. U.S. Pat. Nos. 6,852,446, 6,306,540, 6,489,055, and “Lithium Batteries Science and Technology” edited by Gholam-Abbas Nazri and Gianfranceo Pistoia, KluerAcademic Publishers, 2004, which are hereby incorporated by reference in their entireties, are directed to lithium and lithium ion battery systems.
Advances in electrode materials, electrolyte compositions and device geometries continue to support the further development of Li based electrochemical systems. For example, U.S. Patent Application Publication US2012/0077095, published on Mar. 29, 2012, and International Patent Application publication WO 2012/034042, published on Mar. 15, 2012, disclose three-dimensional electrode array structures for electrochemical systems including lithium batteries.
Despite substantial advances, practical challenges remain in connection with the continued development of Li based electrochemical systems. A significant issue, for example, relates to dendrite formation in primary and secondary lithium and lithium ion batteries. It is generally known that Li deposition in many electrolytes is highly dendritic which make these systems susceptible to problems involving shorting, mechanical failure and thermal runaway. Safety concerns relating to dendrite formation are currently a barrier to implementation of metal Li anodes in rechargeable systems. A number of strategies have been pursued to address safety in connection with dendrite formation, particularly in the context of secondary batteries, including development of non-lithium anodes and internal safety systems able to monitor in real time problems associated with dendrite formation.
As will be generally recognized from the foregoing, a need currently exists for electrochemical systems, such as lithium based or alkaline based batteries, flow batteries, supercapacitors and fuel cells, exhibiting electrochemical properties useful for a range of applications. Specifically, lithium electrochemical systems capable of good electrochemical performance and high versatility for both primary and secondary lithium based batteries are needed.